Web dryer



H. W. FAEBER Jan. 8, 1963 WEB DRYER 5 Sheets-Sheet 1 Filed Jan. 30, 1958m w s m H Tm N mwuim W Mn m A MKQ Jan. 8, 1963 H. w. FAEBER 3,071,365

. WEB DRYER 3 Filed Jan. 30, 1958 5 Sheets-Sheet 2 FIG. 2. v M

TEMPERATURE DISTRIBUTED Y RECIRCULATED AIR RESULTING UNIFORM TEMPERATURI 40 I hlll II II TEMPERATURE DISTRIBU N WITHOUT RECIRCULATIO ROOMTEMPERATURE r FIG. 3.

INVENTOR. lwas WIDTH l HARRY w. FAEBER FIG. 4. BY ELTfZiT;

his ATTORNEYSv Jan. 8, 1963 H. w. FAEBER 3,071,365

' WEB DRYER Filed Jan. 30, 1958 5 Sheets-Sfieet 5 FIG. 5.

TOR; HARRY w. FAEBER his A TTORNEYS.

H. W. FAEBER Jan. 8, 1963 WEB DRYER 5 Sheets-Sheet 4 Filed Jan. 30, 1958his A TTORNEYS Jan. 8, 1963 H. w. FAEBER 3,0

WEB DRYER Filed Jan. 30, 1958 5 Sheets-Sheet 5 FIG. 8.

INVEN TOR.

HARRY w. FAEB ER BY I GEM 4' pa-140K his ATTORNEYS United States3,071,865 Patented Jan. 8, 1963 York Filed Jan. 30, 1953, Ser. No.712,185 7 Claims. (Cl. 34-62) The present invention relates to anapparatus for use in drying materials in web form, and particularly toapparatus for use in drying printed Web material at high speeds.

During the past several years, various devices have been developed fordrying rapidly moving webs and these have been found to be ofconsiderable utility in the printing, paper, photographic film andtextile industries. These devices generally employ the principle ofrapidly moving the web to be dried through a chamber of heated air. Thetemperature of the air in the chamber is generally very high and if theweb were to be exposed to such temperature for a substantial period oftime, burning or charring of the web would occur. However, because ofthe short time of contact, the high temperature air serves only toevaporate the solvent or other volatile material from the web.

One of the principal problems in devices of this nature has been therealization of a uniform temperaturegradi cut across the entire surfaceof the web; Gas or oil. burners are generally employed as a source ofheat, and the products of combustion, together with heated airandsolvent vapors, will follow the web either concurrently orcountercurrently, depending on the nature of the apparatus. In order toprevent escape of the noxious products of combustion as well as thevolatilized solvents, the web drying devices are enclosed, the interiorof the dryer being maintained at a pressure slightly below atmospheric.This has created the additional problem of air leakage along the edgesof the web being dried, with attendant impairment of the dryingoperation in these regions. -Attempts at mechanically sealing thesesources of air leakage have proven ineffective because of the necessityof maintaining running clearance between the edges of the web and theenclosure, means of entry into the interior of the dryer for purposes ofrepair and maintenance, and entry and exit of the running web. Where theair leakage is cornpensated for by increasing the drying temperature,scorching of the central portion of the web tends to occur.

An additional difi'iculty involved in the use of presently available webdrying apparatus is the large amount of heat lost by radiation as wellas in the exhaust stack. In order to reduce the air-conditioningrequirements of the room in which the dryer is located, it is necessaryto reduce the amount of makeup air entering the dryerfrom the pressroomto replace the exhausted air, and to provide some means of cooling theexterior surface of the dryer, particularly the top surface thereof.Conventional top surface cooling means include a water-jacketed topportion, and the heat thus removed constitutes a further loss of energyfrom the system.

It is therefore an object of the present invention to provide a means ofobtaining an even temperature across a moving web during drying thereof.

It is another object of the invention to provide a sys-' tem of theabove character in which heated air is directed to a burner enclosure toequalize temperatures across the web.

It is a further object of the invention to provide a system of the abovecharacter in which hot air is withdrawn from a Web heater andsubsequently directed to the web to equalize temperatures thereacross.

Another object of this invention is to provide means any tendency forair to leak into this enclosure.

for reducing the total amount of heat required in operating a web dryingmechanism. Still another object of this invention is to reduce theamount of air drawn from the press-room, thus reducing the airconditioning or air heating load on the pressroom ventilation system. i

These and further objects of the invention are accomplished by disposinga suitable air distributing duct above a rapidly moving web being driedby heating means such as gas burners. The air directing duct has meanstherein for regulating the amount of air distributed to differentportions of the web transversely thereof. The regulating means aredesigned to furnish air to the web where required, in order to provide atemperature curve which, when combined with a temperature curveresultingfrom the primary heating means, minimizes temperaturevariations across the web and affords a desirable temperature curveacross the width of the web.

In a preferred embodiment of the invention, the heated air directed tothe web is provided by withdrawing heated air from the drying chamberadjacent one of the heating means and recirculating it to thedistributing duct. The amount of air furnished to the distributing ductis sufiicient to substantially equalize the pressure between the insideand outside of the burner box in order to reduce However, it ispreferable to maintain a slightly decreased pres sure in the burner boxto prevent the leakage of fumes therefrom.

In a further preferred embodiment, the heated air is withdrawn fromadjacent the center line of the drying chamber and recirculated to adistributing duct. This has the effect of further reducing thetemperature in the central portion of the web and, when used incombination with the means for regulating the amount of air returned tothe web transversely thereof, provides a very effective and easilyregulated means for obtaining a desirable temperature curve havingminimum variations across the width of the web.

An additional feature which may be employed in the dryer of thisinvention is means for flowing recirculated air over the top of thedryer enclosure before distributing the air across the web. In thismanner the enclosure is cooled and the heat thus obtained is returned tothe dry-. ing chamber. Furthermore, means may be employed forwithdrawing and exhausting to the atmosphere a portion of therecirculated air after its passage across the top of the dryerenclosure, but before its introduction into the drying chamber.Similarly, the recirculated air may be caused to flow over the burnersto cool the same. Also, adjustable elements such as louvers or nozzlesmay be employed to direct the recirculated air to the surface of theweb.

These and further objects and advantages of the invention will be morereadily understood when the following description is read in connectionwith the accompanying drawings in which:

FIGURE 1 is a View in perspective of a typical web' drying system inaccordance with the principles of the present invention;

FIGURE 2 is a longitudinal section of a heating hood duct constructed inaccordance with the principles of the present invention;

FIGURE 3 is a view in section of a portion of the apparatus shown inFIGURE 2 taken along line 3- and looking in the direction of the arrows;

FIGURE 4 is a schematic diagram showing the improved temperaturedistribution across the web obtained FIGURE 6 is a view in longitudinalsection of the dryer shown in FIGURE 5 taken along the line 66 andlooking in the direction of the arrows;

FIGURE 7 is a view in section of the apparatus of FIGURE 6 taken alongthe line 77 and looking in the direction of the arrows; and

FIGURE 8 is a partial longitudinal section of a further modification ofthe apparatus shown in FIGURE 5.

Referring to a typical embodiment of the invention in greater detailwith particular reference to FIGURE 1, a web .10, with wet ink on itstop side, having been just printed at a printing station, not shown,travels in the direction indicated by the arrow 11 over rolls 12, 13,'14 and 15 to direction shifting roll 16. The rolls 12 to 16 are watercooled and supported by any conventional structure, .not shown in theinterests of clarity. Three burner boxes 18, 19 and 20 to which arerespectively joined connecting hoods 21, 22 and 23 house a plurality ofceramic cup radiant gas burners 24 (FIG. 2) positioned along andextending laterally across the web 10. According to establishedpractices, the supply of fuel :to the burners 24 is controlled inaccordance with the speed of the moving web 10 to heat the web to apredetermined temperature and to preclude scorching thereof. The burners24 are mounted for rotation .in the usual manner so that they areautomatically turned away from the web 10 when the web movement isstopped.

While the burner boxes and hoods enclose the web 10, longitudinalopenings 25 between the vertical sides of the burner boxes andconnecting hoods permit cold air to leak into the enclosed areas abovethe web 10. This air leakage causes uneven heating of the web, asdescribed above. Such air leakage will be increased where a dryingsystem such as that disclosed in copending application Serial No.491,059, filed February 28, 1955, for Web Drying Methods and Apparatus,is utilized.

More particularly, a divergent blade 26 adjacent to the roll 16cooperates with the burner boxes 18, 19 and 20, connecting hood 23 andan exhaust chamber 27 to provide a heated drying chamber in which arapid air flow in the direction of web movement is built up and reachesmaximum velocity as it passes from the connecting hood 23 under theblade 26 into the exhaust chamber 27, where it is exhausted by means ofa duct 28 leading to an exhaust fan (not shown).

Exhausting air at a high rate from the exhaust chamber 27 results insubstantial air leakage through the spaces 25. Accordingly, absent theintroduction of air into the drying chambers, the temperatures acrossthe web 10 will be as shown in curve A of FIGURE 4, the temperatures atthe web edges being relatively low and the temperatures in the middle ofthe web being relatively high.

Branch recirculating air ducts 29, 30 and 31 withdraw air from thecenter of the connecting hoods 21, 22 and 23 and direct it to a mainrecirculating air duct 32. Duct 32a, a main recirculating air duct froma further dryer (not shown), connects with duct 32. A recirculating fanhousing 33, the fan being driven by a motor 34 through a belt drive 35,is joined to the duct 32 and includes an output duct 36 divided into twobranches 37 and 38. The branch 37 is for exhaust purposes while thebranch 38 is further divided into branches 39 and 40, the branch duct 39leading to the (further dryer (not shown).

Recirculated air is directed from the duct 40 through branch ducts 41and 42 into hoods 43 and 44, respectively, distributing air across theweb 10 passing through the burner boxes 19 and 20 in a predeterminedmanner to minimize temperature variations across the web.

Examining a typical hood 43 in greater detail with reference to FIGURE2, a divergent section 45 communicates with a distributing portion 46 inwhich are a plurality of adjustable elements such as vanes 47. Pins 48fastened at each end to the sides of the hood portion 46 are attached tovanes 47 by means of straps 49. The straps 49 join the elements so thatthe vanes 47 may be moved to any desired position and will befrictionally retained there. In this manner recirculated air furnishedto the hood may be distributed to the web 10 in any desired manner.

In operation, the rapidly moving web 10 is heated when passing under theburner boxes 18, 19 and 20 and the boundary layer of air travelling withthe web is separated therefrom by the divergent blade 26 and exhaustchamber 27. Heated air from above the center of the web 10 is withdrawnthrough air ducts 29, 30 and 31, the duct 32, and pumped by therecirculating fan 33 through the ducts 38, 40, 41 and 42 to the hoods 43and 44. The total amount of air circulated may be controlled byconventional dampers (not shown), located in ducts 36, 37 and 38. Theair from the hoods entering the burner boxes 19 and 20 is distributed byadjustment of vanes 47 across the web 10 to provide a temperature curveB, shown in FIGURE 4, which represents the approximate temperaturedistribution over the web that would prevail due to the recirculatedwarm air without burners. Since the recirculated air introduced into thedrying chamber is heated to a lower temperature than the exhausted air,

' greater amounts of such air are furnished to the web center to reducethe temperature of that area. When the curves A and B are combined, aresultant curve C is provided illustrating the flat temperaturedistribution across the web 10, promoting rapid and even drying withoutscorching. The fact that the extremes of the curve C drop off slightlyindicates that a slight negative pressure is maintained in the burnerboxes to prevent the escape of noxious fumes.

It will be observed that the schematic curves A and B as presented inFIGURE 4 are not exact complements. The reason they provide a fiat curveC is due to the change in pressure in the burner boxes which greatlyreduces the amount of cool air drawn in along the edges of the web 10.

Another embodiment of this invention is shown in FIGURE 5. In thisembodiment, the means for supporting and moving the printed web 10 issimilar to that described in copending application Serial No. 491,059,mentioned above. More particularly, this means includes a supportingroll 50 and direction shifting rolls 51, 52, 53 and 54. Roll 51 is acooling roll, and roll 52 is a vacuum roll. In addition, suitable means(not shown) may be provided for rotating the rolls to drive the web 10in accordance with conventional practice in the art.

A plurality of line gas burners 55, 56 and 57 are supported in anydesired manner extending laterally across the top of the web 10.According to established practice, the burners 55-57, inclusive, arecontrolled in accordance with the speed of the moving web 10 to heat thesurface thereof to a predetermined temperature.

The moving web 10 and the supporting roller 50, together with theburners 55-57, inclusive, are enclosed by a suitable hood structurecomprising insulated bottom and side portions 58 and 59, respectively,and a top portion 60. An opening 61 in the hood structure is maintainedto allow entrance of the moving web 10.

An exhaust chamber 62 is positioned adjacent the roll 51 and a divergentblade 63 is positioned above the roll 51 and adjacent the Web 10 tocreate a turbulence in the Zone of air surrounding the moving web, asdescribed in copending application Serial No. 491,059. A seconddivergent blade 64 is supplied adjacent the vacuum roll 52, and a secondexhaust chamber 65 is positioned immediately adjacent the divergentblade 64 and the vacuum roll 52.

The exhaust chambers 62 and 65 are fitted with suitable conduits 66 and67, respectively, which are in turn connected with a blower 68 and anexhaust stack 69. The blower 68 serves to withdraw the exhaust fumesfrom the exhaust chambers 62 and 65 and direct them out of the dryingroom through the stack 69.

The novel exhaust air recirculation system of this embodiment of theinvention comprises a main duct 70 leading from the exhaust stack 69 toa plurality of dispensing hoods 71, each situated directly above aportion of the dryer to be cooled by the recirculated exhaust gases. Aplurality of dampers 72 and 73 are provided in the exhaust stack 69 andthe duct 70, respectively, toregulate the flow of recirculated air. Thehoods 71 lead to a cooling chamber 74 situated directly above the topsurface of the dryer and having a common wall therewith to facilitateheat transfer between the chambers. Atthe end of the cooling chamber 74remote from the hood 71, an opening 75 is provided that communicatesdirectly with the drying chamber 76, as shown in FIGURE 6. The opening75 extends laterally, spanning the entire width of the moving web 10 andcontains a louver 77 whichis positioned so as to direct the recirculatedexhaust gases across the surface of moving web 10. Suitable insulation78 completely encloses the entire exhaust air recirculation system. a

Disposed within the cooling chamber 74 adjacent the opening 75 are aplurality ofvanes 79 which may be of the same design as the vanes 47 ofFIGURE 1. The vanes 79 may be placed in any desired position to regulatethe fiow of recirculated air to minimize temperature variations acrossthe web 10.

Hood 71a and cooling chamber 74a, which feed recirculated air across thefirst section of the dryer and the burners 55 and 56, are of somewhatdifferent design. Cooling chamber 74a has a plurality of openings 75a tothe drying chamber 76. In order to control the distribution of therecirculated air across the web, the vanes 79a are disposed in separatepassageways 80 formed by suitable partitions in the hood 71a and thecooling chamber 74a as shown in FIGURES and 7.

In operation of the dryer embodiment shown in FIG- URE 5, the moving webis heated when passing under the burners 55, 56 and 57 and the exhaustgases are removed through exhaust chambers 62 and 65 to exhaust stack69. The stream of exhaust gases is divided, a portion being exhausted tothe atmosphere and a portion being recirculated through duct 70, hoods71 and 71a, through the cooling chambers 74 and 74a and openings 75 and75a into the drying chamber 76. The air entering the drying chamber isdistributed in any desired manner to minimize temperature variationsacross the web 10 by adjustment of vanes 79 and 79a.

An alternate embodiment of the novel air recirculation system of FIGURE5 is shown in FIGURE 8. This feature comprises means for withdrawing aportion of the recirculated air at a point immediately prior to itsintroduction into the drying chamber and after it has passed over andcooled the top of the dryer, in combination with an independent airrecirculation system. A duct 81 communicating with the cooling chamber74 is mounted on said cooling chamber at a point adjacent the opening75, but offset slightly therefrom. The duct 81 leads to an auxiliaryduct 82 which in turn communicates with a recirculator fan (not shown).In addition, a second duct 83 communicating with the drying chamber 76and with the auxiliary duct 82 is adapted to withdraw exhaust gases fromthe drying chamber. Both the recirculated air from duct 81 and theexhaust gases from duct 83 are returned to the recirculating fan (notshown), whose intake side may also be connected to the discharge side ofthe divergent blade exhanst fan 68 shown in FIG- URE 5 by means of abranch duct from duct 69. Thus, the recirculating fan receives air fromthree kinds of sources; the cooling chambers 74, the exhaust duct 83,and the branch of the divergent blade exhaust.

In the operation of this embodiment and referring to FIGURES Sand 8, theexhaust gases removed from the exhaust chambers 62 and 65 are removedfrom the drying system through the exhaust stack 69. A separate airrecirculating system including a recirculating fan (not shown), ducts 70on the discharge side of the recirculating fan, hoods 71 and 71a,cooling chambers 74 and 74a, and ducts 81, 82 and 83, is employed. Theexhaust gases are removed from the drying chamber through duct 81 bymeans of the recirculating fan (not shown) and returned to therecirculation system through ducts 70, 71 and 71a and the coolingchambers 74 and 74a. The recirculated air passing through the coolingchambers cool the top of the dryer. If desired, a portion of therecirculated air may be withdrawn through ducts 81 after its coolingfunction is completed and exhausted through the recirculating fan. Onthe other hand, duct 81 maybe closed by means of suitable dampers 84,and the recirculated air directed upon the Web. In this case, thedistribution of the recirculated air across the web will be regulated byadjustment of vanes 79, as described with relation to FIGURES 1 and 5.When necessary, additional quantities of air may be drawn into theindependent air recirculation system through the intake side of therecirculating fan, from the exhaust side of fan 68 by means of a branchduct from duct 69. In order to prevent a buildup of the volatile exhaustgases in the recirculation system, a portion of the recirculated gasesis exhausted to the atmosphere, as shown in the recirculation system ofFIGURE 1.

' It will be understood that the above-described embodiments of theinvention are illustrative only and that modifications will occur tothose skilled in the art. Therefore, the invention is not to be limitedto the specific apparatus disclosed herein but is to be defined by theappended claims.

I claim:

1. Drying apparatus for moving webs comprising a drying chamberextending across and communicating with one side of the web, the sidesof the chamber being spaced from the Web sides, web heating means in thechamber, means to exhaust heated air from the chamber which creates apressure below atmospheric in the drying chamber and causes air to flowinto the chamber through the spaces between the chamber sides and theweb sides toward the center of the web, such air flow tending to createan uneven temperature distribution across the web with the web center ata high temperature relative to the web side temperature, means tointroduce air into the drying chamber to raise the pressure therein andreduce the pressure ditferential between the drying chamber and theatmosphere, and means to distribute the introduced air nonuniformlyacross the web under the chamber in a pattern to compensate for theuneven temperature distribution and minimize temperature variationsacross the web.

2. Apparatus as defined in claim 1, wherein said means to introduce aircomprises a duct, and said means to distribute the introduced aircomprises adjustable elements to control the distribution pattern of theair across the web.

3. Apparatus as defined in claim 1, in which means are provided torecirculate at least a portion of the exhaust air and use it for atleast a portion of the air introduced into the drying chamber.

4. Drying apparatus for moving webs comprising a drying chamberextending across and communicating with one side of the web, the sidesof the chamber being spaced from the web sides, web heating means in thechamber, means to exhaust air from the drying chamber which causes airto flow into the chamber through the spaces between the chamber sidesand the web sides, a cooling chamber outside of and parallel to thedrying chamber, a wall common to the cooling chamber and the dryingchamber, the common wall being cooled by the cooling chamber to reduceheat radiation from the drying chamber, means to recirculate at least aportion of the exhaust air through the cooling chamber, and means tointroduce at least a portion of the recirculated air into the dryingchamber to raise the pressure therein and reduce the pressuredifferential between the drying chamber and the atmosphere.

5. Apparatus as defined in claim 4, in which is provided means towithdraw a portion of the recirculated air from the cooling chamberafter its cooling function has been completed and prior to itsintroduction into the drying chamber.

6. In web drying apparatus, a drying chamber adapted to receive a movingweb, the drying chamber including heating means to dry the moving web, acooling chamber outside the drying chamber and parallel to the movingweb, a wall common to the cooling chamber and the drying chamber, thecommon wall being cooled by the cooling chamber to reduce heat radiationfrom the drying chamber, means for recirculating air through the coolingchamber into the drying chamber, and means for selectivelywithdrawingair from the cooling chamber and from the drying chamber inpredetermined amounts and returning the air to the intake side of therecirculating means.

7. In web drying apparatus, a drying chamber adapted to receive a movingweb, the drying chamber including heating means to dry the moving web,means for removing a boundary layer of air from the web after the webhas left the drying chamber, a cooling chamber above and adjacent to thedrying chamber, means for recirculating air through the cooling chamberand into the drying chamber to reduce heat radiation from the dryingchamber, means for selectively withdrawing predetermined amounts of airfrom the cooling chamber, from the drying chamber adjacent the web andfrom the means for removing a boundary layer of air from the Web outsideof the drying chamber, and means for returning the cooling chamber air,the drying chamber air and the boundary layer air to the intake side ofthe recirculating means.

References Cited in the file of this patent UNITED STATES PATENTS1,676,091 Kemp July 3, 1928 2,022,593 Fuykers Nov. 26, 1935 2,183,298Otfen Dec. 12, 1939 2,204,802 Gessler June 18, 1940 2,229,285 GehnrichJan. 21, 1.941 2,268,988 Hess et a1. Jan. 6, 1942 2,330,395 SullivanSept. 28, 1943 2,803,446 Flynn Aug. 20, 1957 2,837,830 'Fry et a1. June10, 1958 2,921,778 Ruif Jan. 19, 1960 2,929,153 Fry et al. Mar. 22, 19602,939,222 Svarar et a1. u- June 7, 1960'

1. DRYING APPARATUS FOR MOVING WEBS COMPRISING A DRYING CHAMBEREXTENDING ACROSS AND COMMUNICATING WITH ONE SIDE OF THE WEB, THE SIDESOF THE CHAMBER BEING SPACED FROM THE WEB SIDES, WEB HEATING MEANS IN THECHAMBER, MEANS TO EXHAUST HEATED AIR FROM THE CHAMBER WHICH CREATES APRESSURE BELOW ATMOSPHERIC IN THE DRYING CHAMBER AND CAUSES AIR TO FLOWINTO THE CHAMBER THROUGH THE SPACES BETWEEN THE CHAMBER SIDES AND THEWEB SIDES TOWARD THE CENTER OF THE WEB, SUCH AIR FLOW TENDING TO CREATEAN UNEVEN TEMPERATURE DISTRIBUTION ACROSS THE WEB WITH THE WEB CENTER ATA HIGH TEMPERATURE RELATIVE TO THE WEB SIDE TEMPERATURE, MEANS TOINTRODUCE AIR INTO THE DRYING CHAMBER TO RAISE THE PRESSURE THEREIN ANDREDUCE THE PRESSURE DIFFERENTIAL BETWEEN THE DRYING CHAMBER AND THEATMOSPHERE, AND MEANS TO DISTRIBUTE THE INTRODUCED AIR NONUNIFORMLYACROSS THE WEB UNDER THE CHAMBER IN A PATTERN TO COMPENSATE FOR THEUNEVEN TEMPERATURE DISTRIBUTION AND MINIMIZE TEMPERATURE VARIATIONSACROSS THE WEB.